The
Midwest was a place of environmental tumult, forming and reforming
in shifting equations of ice and water, climate and topography. Before
people arrived, hundreds of thousands of years of advancing and retreating
glaciers scoured the land—until a warming trend loosened the cold’s
grip. The first midwesterners likely arrived by 13,500 years ago, probably
from the northwest or west. Roughly the northern half of Minnesota was
under a mantle of ice, as was upper Wisconsin and much of Michigan.

Further south the Great Lakes overflowed with glacial melt. Occasional bouts of frigid, dry weather would temporarily reverse the process, and the shore expanded. The topography was in near-constant flux, with what has been called an “accordion of habitats.” Some witnessed this ebb and flow in their lifetimes.